In recent years, organic compounds having semiconductor characteristics have attracted attention. Among the organic compounds, a polyacene compound such as pentacene and tetracene has been known as an organic semiconductor material due to high carrier mobility thereof for many years. In addition, “carrier mobility” herein is used in a broad sense, including electron mobility and hole mobility.
However, publicly known polyacene compounds have low solubility in a solvent, and therefore film formation by an application process, a printing process or the like is difficult. Therefore, a device (hereinafter, also referred to as “device”) having semiconductor characteristics is forced to be prepared according to a vapor deposition process requiring high manufacturing cost. Further, the publicly known polyacene compounds also have a problem on chemical stability such as oxidation resistance, and therefore is a difficult material from a viewpoint of industrial practicality.
Consequently, in order to improve the solubility and the chemical stability, study has been conducted on compounds in which various kinds of substituents are introduced on an acene skeleton (see Patent literature No. 1 and Non-patent literature No. 1, for example). Further, study has been already conducted on compounds in which chalcogen such as sulfur and selenium is introduced on a part of an acene skeleton, for example, dibenzothienothiophene (BTBT) and dinaphthothienothiophene (DNTT) (see Patent literature Nos. 2 to 3, for example).
According to the Patent literature described above, success has been made in improving the chemical stability in the compounds while high carrier mobility is maintained. However, the compounds are linear and have highly symmetrical molecular structure, and therefore have a problem of solubility being not necessarily sufficient even if a substituent such as an alkyl group is introduced thereon, or the like. Moreover, as the molecular structure becomes further complicated, the compounds can be barely synthesized using an expensive raw material or a reactant having a high environmental load, and through multi-step synthesis.
Thus, various kinds of organic compounds having semiconductor characteristics have been developed so far. However, development has not sufficiently been made yet for an organic compound having excellent chemical stability, high solubility in a solvent and high carrier mobility (material that can be applied or printed in a solution state, and can be applied to a wide range of uses, such as transistor preparation).
Therefore, organic semiconductor materials having as a basic skeleton a nonlinear molecule having low symmetry rather than a linear type have attracted attention in recent years. Specific examples include a compound having V-shaped or U-shaped structure, such as dinaphthofuran, dinaphthothiophene, dianthrafuran and dianthrathiophene. Basic skeletons thereof (unsubstituted compounds) have been already publicly known (see Patent literature Nos. 4 to 5, Non-patent literature Nos. 2 to 6, for example). However, while the compounds are excellent in chemical and thermal stability, the compounds have a problem of poor solubility in a solvent.
Several examples of compounds in which a substituent is introduced on the skeleton have been already disclosed (see Patent literature No. 6 and Non-patent literature No. 7, for example). Patent literature No. 6 refers to a dinaphthothiophene derivative on which four to twelve alkyl groups or phenyl groups are introduced, and an organic film including the derivative. However, Patent literature No. 6 discloses no synthesis example of the derivative at all, and has no description at a degree according to which a so-called person skilled in the art can understand a method for manufacturing the derivative, and thus the derivative is not substantially disclosed therein. Moreover, no verification has been made for solubility of the derivative in any solvent, application properties of a solution containing the derivative, and semiconductor characteristics of the derivative, and an effect due to introduction of the substituent thereon is also unknown. In addition thereto, no disclosure has been made on a compound itself for a dinaphthothiophene derivative on which one to three alkyl groups or phenyl groups are introduced. Further, Non-patent literature No. 7 discloses a dianthrathiophene derivative represented by the formula described below, but no verification has been made on the semiconductor characteristics in a similar manner.
wherein, Bu is butyl.